21268240 has 80 divisors (see below), whose sum is σ = 57103488. Its totient is φ = 7216128.

The previous prime is 21268231. The next prime is 21268249. The reversal of 21268240 is 4286212.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (21268231) and next prime (21268249).

It is a tau number, because it is divible by the number of its divisors (80).

It is not an unprimeable number, because it can be changed into a prime (21268249) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 91164 + ... + 91396.

Almost surely, 2^21268240 is an apocalyptic number.

21268240 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21268240, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28551744).

21268240 is an abundant number, since it is smaller than the sum of its proper divisors (35835248).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21268240 is a wasteful number, since it uses less digits than its factorization.

21268240 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 416 (or 410 counting only the distinct ones).

The product of its (nonzero) digits is 1536, while the sum is 25.

The square root of 21268240 is about 4611.7502100613. The cubic root of 21268240 is about 277.0621398731.

The spelling of 21268240 in words is "twenty-one million, two hundred sixty-eight thousand, two hundred forty".